Image pickup apparatuses fire a flash so as to adjust the amount of light when capturing an image of a subject under low illuminance conditions. Some image pickup apparatuses that capture an image using a solid-state image pickup device have a function of performing preliminary light emission using a flash and detecting and analyzing the amount of light reflected from a subject to calculate the appropriate amount of light required for main light emission.
CCD (Charge Coupled Device) image sensors have been mostly used as an image pickup device for an image pickup device. However, as the number of pixels included in a solid-state image pickup device becomes increased, CMOS (Complementary Metal Oxide Semiconductor) image sensors are currently attracting attention. A CMOS image sensor has features in which pixel signals can be randomly accessed and can be rapidly read out compared with a CCD image sensor and it has high sensitivity and consumes low power.
However, in known image pickup apparatuses using a CMOS image sensor, reflected light caused by preliminary light emission of a flash is transmitted to only a part of the whole area of a solid-state image pickup device, since exposure times of individual pixels are different from each other. Accordingly, it is difficult to accurately calculate the amount of light required for main light emission. In order to overcome this difficulty, there is an image pickup apparatus in which a part of the whole area of a solid-state image pickup device is set as a metering area and preliminary light emission is performed during the electric charge storage time of photoelectric conversion elements included in the metering area to allow the metering area to accurately receive reflected light caused by the preliminary light emission (see, for example, Japanese Unexamined Patent Application Publication No. 2000-196951 (paragraphs [0018] to [0026] and FIG. 2).